Charles Leonard Hamblin (1922-1985) was an Australian philosopher and one of Australia’s first computer scientists. His main early contributions to computing, which date from the mid 1950s, were the development and application of reverse polish notation and the zero-address store. He was also the developer of one of the first computer languages, GEORGE. Since his death, his ideas have become influential in the design of computer interaction protocols, and are expected to shape the next generation of e-commerce and machine-communication systems.

Hamblin was born in 1922 and attended North Sydney Boys’ High School and Geelong Grammar. He then took degrees in Arts (Philosophy and Mathematics) and in Science (Physics), followed by an MA in Philosophy (First Class Honours) at Melbourne University, with his studies interrupted by work as a radar officer in the RAAF during World War II. Following the war, he gained a PhD at the London School of Economics, University of London on the topic, “Language and the Theory of Information”, apparently under Karl Popper (Hamblin 1957a). Hamblin’s thesis presented a critique of Shannon’s theory of information from a semantic perspective, and developed a possible-worlds semantics for question-response exchanges. Between 1955 and his death in 1985 he was a Lecturer and Professor in the School of Philosophy at New South Wales University of Technology (NSWUT), which later became the University of New South Wales (UNSW).

In 1956, the University purchased a DEUCE computer manufactured by the English Electric Company (EEC), an early British computer manufacturer, and Hamblin, with his radar background, became involved in working with this machine. This was the second academic computer in Australia, after that of the University of Sydney. Hamblin soon became aware of the problems of (a) computing mathematical formulae containing brackets, and (b) the memory overhead in having and dealing with memory stores each of which had its own name. One solution to the first problem was Jan Lukasiewicz’s Polish notation, which enables a writer of mathematical notation to instruct a reader the order in which to execute the operations (e.g. addition, multiplication, etc) without using brackets. Polish notation achieves this by having an operator (+, *, etc) precede the operands to which it applies, e.g., +ab, instead of the usual, a+b. Hamblin, with his training in formal logic, knew of Lukasiewicz’s work.

However, this does not solve the second problem. Hamblin realized that placing the operation symbol to the right of the operands (i.e., reversing the polish notation, as in ab+) would enable the machine to make use of a store which did not require an address – the current operation would always be conducted on the most-recent operands inserted and still remaining in the store. This store came to be called a stack, or last-in, first-out (LIFO) store. He implemented these ideas in a programming language for the DEUCE machine, a language he called GEORGE, for General Order Generator. This work was undertaken at a time when there were only a handful of programming languages, and indeed still some resistance to the idea of non-assemblor languages (due to their greater memory requirements). Hamblin’s work on the DEUCE machine at UNSW overlapped with that of Gordon Bell and Bob Brigham, who wrote a symbolic assembler and run-time system called SODA (or Symbolic Optimum DEUCE Assembly Program) (Brigham and Bell 1959). GEORGE used the SODA runtime library.

Hamblin presented his work at the first Australian conference on computing, which was held at the Weapon Research Establishment in Salisbury, South Australia, in June 1957 (Hamblin 1957b). Employees of the English Electric Company were present at this conference, and took his ideas back to England. As a consequence, Hamblin’s architecture was implemented in the company’s next machine, which came to be called the KDF9. The architecture of this machine even used Hamblin’s terminology. This machine was announced in 1960 and delivered (i.e. made available commercially) in 1963. Hamblin published his ideas in 1957 (Hamblin 1957b, 1957c) and 1962 (Hamblin 1962). An earlier paper (Burks et al. 1954) presented the same ideas in a more general notational framework, and that paper was briefly reviewed in the Journal of Symbolic Logic in 1955 (Nelson 1955). Hamblin may have seen the Burks paper, or (with greater probability) the JSL review, although neither of these articles is cited in his 1962 Computer Journal paper which presents RPN (Hamblin 1962). (When accessed on 2010-07-20, the catalogue of the Library of the University of New South Wales indicated that the UNSW Library did not currently carry the journal in which the Burks paper was published, Mathematical Tables and Other Aids to Computation; of course, the Library may have carried this journal in the past.)

Another computer, the American Burroughs B5000, announced in 1961 and delivered in 1963, also used a zero-address architecture, and also enabled reverse polish notation to be used for programming. R. S. Barton, one of the designers of the B5000, has written that he developed RPN independently of Hamblin, sometime in 1958 while reading a textbook on symbolic logic, and before he was aware of Hamblin’s work (Barton 1970). A decade after Hamblin first published his ideas, engineers at Hewlett-Packard (HP) developed a personal calculator, the 9100A Desktop Calculator, which used RPN. This calculator, the first in a long line by HP, was released in 1968, and it popularized RPN among the scientific and engineering communities; note, however, that early advertisements for the 9100A did not mention RPN.

Even if Hamblin’s work on RPN was not the first to be published that applied Polish Notation to a computational domain, people at the time thought it was, as evidenced by the refereed publication of his 1962 paper in the Computer Journal, and Barton’s comments published in 1970. Hamblin’s contribution to computer science was also recognized with an obituary in the Australian Computer Journal (Allen 1985) and in an influential history of British computing (Lavington 1980). In addition, GEORGE is listed in Bill Kinnersley’s comprehensive directory of computer languages, The Language List. In the 1960s, Hamblin also worked on implementing Tarski’s decision method for real closed fields (Tarski 1951), the first order theory of real numbers with addition and multiplication, and hired two programmers to assist in this project, Malcolm Newey and Vaughan Pratt. However, only in 1974 was it shown by Fischer and Rabin (1974) that the running time of this problem had an exponential lower bound.

Although usually not credited, Hamblin was the originator of two other ideas which subsequently became important in Artificial Intelligence. Firstly, Hamblin appears to have been the first person to define a formal measure of plausibility, distinct from that of probability, in a paper published in 1959. Alternative formalisms for uncertainty have come to play a very important role in Artificial Intelligence, particularly in the design of knowledge-based systems, due to the failure of the standard Kolmogorov axioms of probability to adequately account for all forms of uncertainty and for its manipulation. One person particularly taken by Hamblin’s work in this area was the British economist, George Shackle, who in the 1940s and 1950s had developed a theory of decision-making under uncertainty based on the potential surprise of rival uncertain beliefs, and focusing on the best-case and worst-case outcomes of alternative decision-options (see pp. 97 – 100 of Shackle 1969). (Shackle’s theory, based on his real-world experience of government economic policy making and business investment decisions, differed from the Maximum Expected Utility theory of Leonard J. Savage which has unfortunately come to dominate mainstream economics.)

Secondly, Hamblin was the first person to propose an axiomatic account of time based on intervals, rather than points. This was in a paper published in 1969. An interval calculus for time was later proposed by James Allen (1984), and has been influential in AI, both as a basis for reasoning about time, and, when extended to multiple dimensions, as a basis for reasoning about space (Anger and Rodriguez 1991).

From the 1960s, Hamblin returned to work in philosophy, particularly the philosophy of argumentation, and wrote two very influential books. One of these, Fallacies, published in 1970, is a study of the classical logical fallacies, such as begging the question, which Hamblin examined by means of formal dialogue games. These are games between speakers who utter statements according to strict rules, and they were first studied by Aristotle. Being rule-governed, these games have gained the attention of computer scientists, and, from about 1989, they have been applied in a number of areas, including: natural language processing; human-machine interaction; the design of complex software; and for dialogues between autonomous software agents (McBurney and Parsons 2009). Interaction and communication protocols based on formal dialogue games are likely to form the basis for the next generation of e-commerce systems and systems supporting high-level machine-to-machine communications. Another of Hamblin’s books, Imperatives, published posthumously in 1987, has also been influential in recent work in computer science, in modeling and implementing delegation of tasks between software agents (Atkinson et al. 2008, Reed and Norman 2007, Norman and Reed 2010).

Hamblin was fluent in several languages, including ancient Greek and Latin. He was one of three fellow-students from his time at Geelong Grammar to become professors of philosophy (the others being David Armstrong and Michael Scriven). At the time of his death, he was apparently attempting to set text of Wittgenstein to music.

Charles Hamblin was a pioneer computer scientist and a prominent philosopher, whose influence on the subject is still being felt. His contributions to applied and theoretical computing show the deep links which Computer Science has had, and continues to have, with philosophy and logic.

References:

In addition to the works cited in the text above, I have also listed all of Hamblin’s publications known to me.

C. L. Hamblin [1957b]: An addressless coding scheme based on mathematical notation. Proceedings of the First Australian Conference on Computing and Data Processing, Salisbury, South Australia: Weapons Research Establishment, June 1957.

C. L. Hamblin [1964a]: Has probability any foundations? Proceedings of the Symposium on Probability of the Statistical Society of New South Wales, May 1964. Reproduced in Science Yearbook, University of New South Wales, Sydney, 1964.

In compiling this biography, I am grateful for information and support received from: Gordon Bell, Jim Crosswhite, David Hitchcock, Jim Mackenzie, Vaughan Pratt, Michael Scriven, Phillip Staines, Robin Vowels, Doug Walton, and the family of the late Charles Hamblin. The views I express here are, of course, solely my own.

Copyright, 2003-2011. All rights reserved.

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Readers may like to know that the Australian Computer Museum Society web site is at http://www.acms.org.au — and that the ACMS Inc is still searching for Display Space in which to commemorate Australian Computing Pioneers.